The present invention relates to a driving state monitoring apparatus for vehicles, which monitors a driving state of the driver of the vehicle and issuing an alarm as required.
A driving state monitoring apparatus is known which has means for estimating the response delay time of the driver and the deviation between a vehicle position and the running lane according to the amount of steering of the vehicle and the vehicle speed, means for comparing the estimated response delay time of the driver and the estimated deviation with a response delay time and a deviation in a normal condition, respectively, and means for determining the driving state of the driver (e.g., an abnormal steering caused by a lowered driving ability due to dozing or fatigue of the driver) (Japanese Patent Laid-open No. Hei 5-85221).
Also known is a driving state monitoring apparatus having means for detecting the yaw rate and the vehicle speed, means for obtaining a reference line for running of the vehicle according to the detected yaw rate and the detected vehicle speed, and means for determining abnormality of the driving state of the driver by using a parameter indicative of the deviation between an actual running locus and the reference line (Japanese Patent Laid-open No. Hei 8-249600).
However, in the above-mentioned conventional monitoring apparatus described in Japanese Patent Laid-open No. Hei 5-85221, the deviation between the actual vehicle position and the running lane (reference vehicle position) is calculated according to the amount of steering and the vehicle speed, but not according to a physical quantity relating directly to vehicle behavior. Accordingly, an error in this deviation can be produced due to changes in vehicle characteristics (e.g., characteristics of the vehicle suspension or the steering device), causing a reduction in accuracy of determination of the driver""s driving state.
On the other hand, in the monitoring apparatus described in Japanese Patent Laid-open No. Hei 8-249600, the driving state is determined by using the yaw rate relating directly to vehicle behavior, thereby improving the determination accuracy. However, the quantity of computation for the calculation of the reference line as a determination reference is large, so that a microcomputer dedicated solely to the monitoring of the driving state is required. Accordingly, it is difficult to reduce the number of microcomputers used in the monitoring apparatus for the purpose of cost reduction.
It is accordingly an object of the present invention to provide a driving state monitoring apparatus which can precisely grasp the behavior of a vehicle with a smaller quantity of calculations as compared with the prior art, thereby effecting precise determination of the driving state.
In accordance with the present invention, there is provided a driving state monitoring apparatus for a vehicle, for monitoring the driving state of a driver of the vehicle, comprising: behavior parameter detecting means for detecting a behavior parameter indicative of a quantity of lateral movement of the vehicle; vehicle speed detecting means for detecting the speed of the vehicle; behavior reference setting means for obtaining a simple regression line according to changes in the behavior parameter and setting the simple regression line as a behavior reference; lateral deviation behavior quantity calculating means for calculating the lateral deviation behavior quantity of the vehicle according to the behavior parameter, the behavior reference, and the vehicle speed; driving state determining means for determining whether or not the driving state of the driver is proper according to the lateral deviation behavior quantity; and road shape determining means for determining the shape of a road on which the vehicle is running; wherein when the road shape determining means determines that the road is substantially straight or curved with a substantially constant radius of curvature, and the driving state determining means determines that the driving state of the driver is not proper, it is determined that the driving state of the driver is abnormal.
With this arrangement, a simple regression line is obtained according to changes in behavior parameters indicative of lateral movement of the vehicle, and this simple regression line is set as a behavior reference. Further, a lateral deviation behavior quantity of the vehicle is calculated according to the behavior parameter, the behavior reference, and the vehicle speed. Then, it is determined whether or not the driving state of the driver is proper according to the lateral deviation behavior quantity. When it is determined that the road on which the vehicle is running is substantially straight or curved with a substantially constant radius of curvature, and it is further determined that the driving state of the driver is not proper, it is determined that the driving state of the driver is abnormal.
The simple regression line as the behavior reference can be obtained with a relatively small quantity of calculation, so that the quantity of calculation can be reduced compared with the prior art apparatus, and the driving state can be monitored without the use of a microcomputer dedicated to the driving state monitoring. As a result, the driving state can be monitored by using a microcomputer provided in another system (e.g., a navigation system), thereby effecting a cost reduction. In the case where the road shape is largely changed, the lateral deviation behavior quantity tends to increase because of the use of the simple regression line as the behavior reference. In consideration of this tendency, the determination of abnormality is performed under the conditions that the road is substantially straight or curved with a substantially constant radius of curvature. Therefore, although the simple regression line is used as the behavior reference, the driving state can be precisely determined.
Preferably, the road shape determining means estimates a radius of curvature of the road on which the vehicle is running and determines the shape of the road according to the estimated radius of curvature and a change rate of the estimated radius of curvature.
Preferably, the lateral deviation behavior quantity calculating means calculates a running locus of the vehicle according to the behavior parameter and the vehicle speed, calculates a lateral deviation of the running locus with respect to the behavior reference, and calculates a maximum amplitude of the lateral deviation during a predetermined time period as the lateral deviation behavior quantity.
As a modification, the lateral deviation behavior quantity calculating means calculates a running locus of the vehicle according to the behavior parameter and the vehicle speed, and calculates the area of a region surrounded by the running locus and the simple regression line as the lateral deviation behavior quantity.
More preferably, the road shape determining means estimates the radius of curvature according to the vehicle speed and a regression coefficient of the simple regression line.
Preferably, the driving state determining means sets a threshold for use in determining whether or not the driving state is proper, according to the vehicle speed.
More preferably, the driving state determining means sets a threshold for use in determining whether or not the driving state is proper, according to the vehicle speed and the estimated radius of curvature.
As a modification, the driving state determining means calculates a statistic including at least a mean value from a plurality of measured data of the lateral deviation behavior quantity, and sets a threshold for use in determining whether or not the driving state is proper, according to the calculated statistic.
Preferably, the driving state determining means determines whether or not the driver intends to make a lane change, and when the driving state determining means determines that the driver does not intend to make the lane change and that the driving state is not proper, it is determined that the driving state is abnormal.